Cutter spacing checker



y 12, 1953 G. H. HEDM'AN 2,637,908

vCUTTER SPACING CHECKER Filed April 26, 19.45 3 Sheets-Sheet l MVi/V/"Wz? J 90.31am? f/ 64 4mm y 1953 G. H. HEDMAN 2,637,908

CUTTER SPACING CHECKER Filed April 26, 1945 3 $heets--Sheet 2 & @ZZ% May 12, 1953 G. H. HEDMAN;

CUTTER SPACING CHECKER 3 Sheets-Sheet 3 Filed April 26, 1945 Patented May 12, 1953 UNITED STATE-g r QFFICE CUTTER. SPACING CHECKER Application April 26, 1945, Serial No. 590,482

5 Claims.

The present invention relates to a device or apparatus for accurately checking the tooth. spacing on rotary shaper type cutters, for gen* erating gears or other toothed elements. hav ihg', substantially accurately spaced increments around the periphery thereof to determine the uniformity of the spacing between. the teeth and the sameness of the helicoidal teeth surfaces at arbitrary distances from either the crown or base of the teeth.

The primary object of the invention is to pro vide a device of the character set forth with which accuracy of measurement will approach 30005 inch. A further object is to provide a device of the character set forth with which, after a cutter or other member to be tested is mounted thereon. and trued up, operation is entirely autm matic, it being only necessary to plot or record the indicator readings. A further object is to provide such device wherein errors, due to variations in pressure exerted upon the member being tested or in the. speed of operation or discrepancies which are inherent in manually operated devices due to the personal factor of different individuals, are completely eliminated.

The foregoing and. other objects not specifically enumerated are accomplished with thev device of the present invention, the construction and operation of which will be understood from the de tailed description which follows when consider ed in connection with the accompanying drawings showing a preferred embodiment, and wherein:

Figure l is a front elevation, with parts broken of the cutter spacing checker forming the subject matter of the present invention.

Z is a top plan view of the cutter spacing check-er shown in Fig. l.

3 is a section taken substantially along the plane of the line 3-3 of Fig. 1.

Fig. i is a section taken substantially along the plane of the line l-i of Fig. 3.

Fig. 5 is a section. taken substantially along the plane of the line 5-5 of Fig. 2.

Referring to the drawings, in the various figures of which the same reference characters are employed to designate corresponding parts, the numeral it represents a base, herein shown'of elongate or oblong form, having mounted in the underside thereof a plurality of leveling screws H. Projecting upwardly centrally of the base is a hub 62 having an axial bore therethrough in which is positioned a dead center i3 which is adjustable vertically, such adjustment being accomplished by means of a hand wheel is which in a circular T-slot 39.

screw-threadedly engagesv the dead center, the. hand wheel being held against axial movement with respect to the base by a split rabbeted ring I5. To provide for the axial non-rotative movement of the dead center as the hand wheel 14. is

rotated, and for locking the dead center in desired relation to the base, the dead center is formed with a longitudinally extending groove 16 within which is en ageable an end plug ll fitted into the end of a thumb screw i8 which is screwthreaded into the base ill.

, Rotat-a-bly mounted upon the base in concentric relation to the hub i2 thereof is a circular tabl I9 which is supported on a pair of large precision pre-loaded ball bearings Zli which are held on the hub by a circular spanner nut. 2.! threaded into the top face of the table. A 010- sure plate 2?. may be mounted over the spanner nut 2i to cover the openings therein and preclude the entrance of foreign matter into theraces, of the bearings 2o. Supported on the base It is a yoke 23 which has mounted in the crown thereof a spring-loaded center 24, the spring load thereon being adjustable by a thumb-screw 2.5 which bears upon a compression spring 26 mounted within a bushing 27 within which the center M is held.

The dead center 53 and the spring-loaded center 2c are adapted to have mounted therebetween an arbor 28 upon which may be mounted a gear shaped member 29, for example, a gear shaper cutter, the spacing between the teeth of which is to be checked. For facilitating the positioning of the arbor with the gear shaped member thereon between the centers of i3 and 24, the latter is mounted so that it may be quickly raised and lowered. To accomplish this the bushing 21 is formed with a longitudinally extending rack 30 in mesh with which is a pinion Ill mounted on a shaft 32 extending transversely through the yoke and having at its outer end an operating thumb wheel 33. The bushing El is slidably mounted within a second bushing 34 mounted within the crown of the yoke 23 and held therein by a spanner nut 35. The bushing 3 has a limited amount of radial play in the yoke so that the bushing 21 which carries the upper center 29 may be accurately aligned with the dead center To accomplish this, there are provided an upper and a lower set of radiallydisposed set screws Eifi adjustable through the crown of the yoke for engagement with the bushing 34.

Carried by the circular table l9 are a pair of yoke-shaped brackets 31 and 38 each mounted As herein shown, the

table is provided with two concentric T-slots 39 and 39a which are machined in the table top at diameters suitable for checking gear shaper cutters of four inch and six inch pitch diameters, respectively, although cutters of intermediate sizes can be handled in a manner to be presently described. For quickly locking and releasing the brackets 31 and 38 so that they may be adjusted angularly about the table, they are connected to the table by a bolt 40, the head of which is non-rotatably positioned within the cross-head of the T-slot and the stud of which bolt extends upwardly through the base of the bracket and is engaged by a clamping nut 4| to which an operating handle 42 is attached, the said nut 4| being positioned within a recess 43' cut into the side of the bracket. The brackets 31 and 38 each carry a horizontal finger 43 which is pivotally mounted between hardened centers 44 and 45, the former being fixed with respect to the bracket and the latter being screw-threadedly adjustable through the crown of the bracket yoke. The inner ends of the fingers 43 are axially bored to receive a hardened pin 46 with a ball-shaped end, said pin being adapted to be clamped within the finger by a thumb-screw 41. The ball-headed pins 46 may be of different lengths to accommodate different pitches of cutters. The outer ends of the horizontal pivoted fingers 43 are also formed with substantially ball-shaped ends to provide contacting surfaces with cooperating members, to be presently described. The outer end 50 of the finger 43 carried by the bracket 31 is adapted to make contact with a small circular disc 48 which is mounted slightly eccentric on a stud 49 carried by the bracket 31, the slight eccentricity of the disc mounting 48 serving to provide a means of fine adjustment for setting the amount of indicator movement (to be presently described) when checking the spacing error by the simple expedient of rotating the disc on the stud and clamping the disc in adjusted position. The outer end 50 of the finger 43 which is mounted in the bracket 38 is adapted to contact the needle 50 of a precision type bellows indicator which is graduated to .0001 inch. Both the circular disc 48 and the indicator 5! are mounted on their respective brackets so that they may be easily released by loosening a clamping nut 52 to which is attached an operating handle 53 and swung through an arc of 180. To hold the disc 48 and/or the indicator 5| in either of their adjusted positions 180 apart, any suitable means such as a spring-pressed ball 54 for engaging in a detent 55, as best shown in Fig. 5, may be employed. The center line passing through the circular disc 48 and its mounting bracket, and the center line passing through the indicator 5| and its needle 50', normally occupy positions substantially at right angles to the respective horizontal fingers 43 which cooperate with the disc 48 and the indicator 50'. For holding each of the fingers 43 in a radial position in relation to the axis through the centers upon which the arbor is mounted, a light spring 55 is provided, one end of which is anchored to a stud 51 mounted on the finger, and the other end of which is attached to a screw 58 threadedly mounted in a yoke-like member 59 carried by the yoke-shaped brackets 31 and 38, respectively. The 180 apart adjustment of the horizontal fingers is desirable so that both flanks of the teeth on the piece to be checked may be accomplished without the necessity of removing the piece from the device and turning it over. Carried by each of the brackets 31 and 38 and extending radially outwardly with respect to the table in a plane substantially coincident with the horizontal plane of the fingers 43 is a bent wire spring 60 (Fig. 1) adapted to engage the radially outward portion of the pivoted finger so as to hold the inner ball end of said finger out of the field of movement of the piece to be checked mounted on the arbor, in the course of positioning the arbor between the centers I3 and 14.

After positioning the arbor together with the piece to be checked between the centers, it is necessary to true up the piece to be checked, both horizontally and axially, and for aiding in accomplishing this there is supported on a fixed part of the machine, preferably on the yoke member, a second indicating member 6|. As herein shown, the indicator BI is carried by a depending rod 62 which is adjustable about its axis and vertically between a pair of clamping jaws 63 mounted on the face of the yoke crown and adapted to be clamped by a thumbscrew 64. Lateral adjustment of the indicator 6| with respect to the rod 62 is accomplished through the medium of a transverse rod 65 carried by the indicator and adapted to be clamped to the rod 62 by a clamping screw 66. The indicator BI is of a type having an indicator needle 61 which may be swiveled through an arc of so that indicator read-- ings may be obtainable at any position of this arc. In view of the axial, vertical and transverse adjustability of the indicator 8|, it will be appreciated that practically any vertical, horizontal or radial position is obtainable, Wherefore it is only necessary to set the indicator needle in an approximately horizontal position and adjust the rods 52 and 65 so that the indicator will contact the back face 68 of the cutter 29. The indicator needle can then be set in a vertical position and moved over to contact the cylindrical edge 69 of the cutter so that, upon rotating the cutter on its arbor by hand and taking indicator readings at various points about a circle on the back of the cutter and at various points around the cylindrical surface 69, the cutter to be checked can be accurately positioned for the checking operation.

Mounted or secured to the base It in any desired manner is a small constant speed motor 70 adapted to rotate through suitable speed reducing means, a crank disc H at a predetermined steed, say of approximately 12 R. P. M. The ..nk disc is formed with a slideway 122 in. which is slidable a pitman '13, to which is connected one end of an adjustable crank arm 14, to other end of which is pivotally connected to a bracket 15 which is attached to the edge of the rotatable table I9 so that upon rotation of the motor, an oscillatory motion is imparted to the table in a horizontal plane. The magnitude of this oscillatory motion will be varied to suit the pitch of the piece to be checked.

In the operation of the device, the gear shaper cutter 29 or other gear shaped member, the tooth spacing of which is to be checked, is mounted with its rear face upon the arbor 28 and placed between the centers I 3 and 24. The height of the piece to be checked is adjusted vertically by rotating the hand wheel [4 until the cutter teeth will assume a position to contact the ball pins-46 carried by the horizontal fingers 43. During this preliminary positioning of the arbor the pivoted fingers 43 are held out of operative position by engagement in the spring clip 50 so as to avoid danger of bumping or jamming the mechanism of the sensitive indicator 5|. The cutter is then checked for eccentric runout upon its arbor and also for trueness on this back face by rotating the cutter by hand and taking readings around the back face 58 and the cylindrical shoulder 69 with the indicator iii and necessary adjustments of the arbor between the centers to insure accuracy in the space checking operation. The pivoted finger at which is mounted in the bracket 3? is then released from its spring clip and allowed to assume its normal radial position in a tooth space. The bracket supporting said finger is then moved in the T-slot so that the ball point it at the inner end of the finger contacts the flank of the cutter tooth and the outerend of the pivoted finger swings over until it contacts the eccentric disc 68 which acts as a positioning stop. The bracket 3'! is then looked in place. The bracket 38 is then similarly moved in the T-slot and set to contact the flank on the same side of a tooth as the finger on bracket Bl, the number of tooth spaces over which the check is to be made arbitrarily chosen, but it is preferable to set the spacing at one less than half the total number of teeth in the piece to be checked. The approximate position of bracket til being thus determined, it is then moved slightly until the ball point it at the inner end of the finger 43 contests the flank of the tooth selected. Continued movement then causes the outer end of the finger to press against the indicator needle 55) and it is preferable to lock the bracket in position so that approximately one-quarter to one-- half turn will be shown on the indicator dial. The stroke of the crank arm M is then adjusted so that the arc of oscillation of table I!) will be slightly greater than the arc of space between two succeeding cutter teeth. Preferably graduations such as '25 are provided along the crank disc slideway for four inch and six inch PD cutters, directly in diametral pitches, so that it is only necessary to set the crank arm at the diametral pitch corresponding to the pitch diameter and the diametral pitch of the cutter being checked. With the device adjusted as above set forth, rotation of the motor l will oscillate the table through the predetermined and the cutter will be automatically indexed around one tooth at a time until a revolution of the cutter or as many revolutions thereof as desired, are ccmpleted.

The indexing is accomplished in the following manner. On the forward stroke, the ball points at the inner ends of the pivot fingers are drawn against the cutter flanks and the fingers pivot until the outer ends thereof are pushed up against the eccentric disc 48 which acts as a stop, and the indicator needle lill which was previously set to give from one-quarter to one-half turn on the dial. The dial of indicator El is then reset at this point to read 0. Sufficient pressure must be placed upon the centers of the mounting arbor by the spring load adjustment so that the cutter will be held stationary until this point is reached. Continuance of the forward stroke then rotates the cutter in a counter-clockwise direction against the drag of the centers as the positioning finger on the bracket Z-i'l continues to be held bl the eccentric stop disc The indicator reading may be taken at any time between the start of roall tation of the cutter and the end of the forward drive stroke. This reading may be either noted or plotted, as preferred in the individual case. On the return stroke the fingers are automatically moved away from contact with the tooth flanks and as the return stroke continues, the cutter remains stationary due to, the friction on the centers and the rotary movement of the table carries the fingers back so that they pivot in the opposite direction when pushed against the cutter tooth immediately behind the one just checked. Backward movement continues until the positioning and index fingers are pulled. over the tips of these cutter teeth and the light tension springs 56 pull the fingers back into radial position in the tooth spaces immediately behind the original spaces. The return stroke then ends and on the succeeding forward stroke this cycle is repeated. Any variation in the length of the chord between the contacting points of the ball pins 46 and the flanks of the teeth of the original space checked and the succeeding spaces will be shown as a variation from the "0 reading on the indicator.

For checking on the opposite flank of the cutter tooth the indicator 5i and the eccentric disc stop 38 are both swung around so that they contact the outer ends of the fingers 43 on the cpposite sides. The checking operation is then repeated exactly as before, with the variation that the indexing is in the opposite direction.

From the noted or plotted variations of the indicator readings, a tester can readily ascertain the nature of any inaccuracy in the toothed memher which has been checked and the necessary steps taken to correct this error or discard the cutter or gear-shaped member as unfit for further use.

Although accuracy in the running of the rotating table is desirable, it is not essential for exceedingly accurate measurements of spacing since a slight run-out or eccentricity in the ball bearings Ell used for mounting the table has negligible results in the readings obtained on the indicator, as a comparatively short space of arc is used in the actual indicating stroke. By selecting the positioning of the finger-supporting brackets 3? and 38 according to the run-out which may be present in the rotating table, very little indicator drift will be noted in the duration of the actual indicating part of the cycle. If a slight drift or change in indicator reading is noted as each tooth registers, a particular point may be used to take the reading. It is applicants usual practice, however, to take the reading just as the crank drive reaches the end of the forward stroke. This practice assures accurate results in the readings taken.

It will be appreciated and recognized from the foregoing description that after the cutter is mounted and trued up, operation is entirely automatic except for the noting or plotting of the variations of the indicator readings. However, there is no variation due to difierence in pressure exerted, or in speed of operation as is often. encountered in manually operated devices used for accurate checking. The present device also avoids discrepancies usually noticed in manually operated devices when peration is done by differ ent individuals due to personal factors which enter into the testing operation.

The device as described in the foregoing speci fication and illustrated in the accompanying drawings constitutes a preferred embodiment of my invention. It will be understood, however,

that various changes may be made in the device disclosed within the range of mechanical skill and engineering dictates, without departing from the spirit of my invention as defined in the appended claims.

What I claim is:

1. A device for checking or comparing the spaces between a predetermined number of substantially equally spaced teeth on a gear-shaped member, said device comprising means for rotatably supporting the gear-shaped member to be checked, two brackets mounted in adjustable, circumferentially spaced relation about the axis upon which the gear-like member is supportable, a. pivoted finger carried by each of said brackets, spring means biasing the fingers to normally hold them radially of the member to be checked, the inner ends of said fingers being adapted to contact respectively the corresponding faces of the teeth between which the space is to be checked, an eccentrically mounted rotatable disc carried by one of the brackets and constituting an adjustable stop for engaging the outer end of the finger carried by said bracket, an indicating mechanism carried by theother bracket and the outer end of the finger carried by said bracket being operatively associated with the indicating mechanism.

2. A device according to claim 1 wherein the support for the gear-shaped member is an arbor mounted between axially aligned spaced centers for rotation with respect thereto, a table mounted for rotation about the axis passing through said centers and the two brackets being mounted on said table.

3. A device of the character set forth, comprising a base having a work-supporting center, a circular table rotatably mounted on the base in concentric relation to the supporting center, two brackets carried by the table and adjustably positionable relatively to each other circumferentially of the table at equal radial distances from the supporting center, a finger pivotally supported intermediate its ends in each bracket to move in a plane parallel to the table, the inner ends of said fingers being adapted for contacting respectively the corresponding faces on teeth of a gear-like member to be tested when mounted on the work-supporting center, said fingers being biased by spring means to normally extend radially with respect to the table, stop means mounted on one bracket for limiting the pivotal action in one direction of. one of said fingers upon contacting a face of the tooth of the gearlike member to be tested, an indicating mechanism mounted on the other bracket and cooperatively associated with the other finger, and both the stop means and the indicating mechanism being rotatable on their respective brackets through an arc of 180 and adapted to be fixedly held in either of said positions.

4.,A device for checking or comparing the spaces between a predetermined number of substantially equally spaced teeth on a gear-shaped member, said device comprising a rigid frame having a base and a yoke, spaced axially aligned centers in the base and in the yoke between which centers an arbor upon which the gear-shaped member to be checked is adapted to be supported, a circular table rotatably mounted on the base in concentric relation to the axis through the centers, means for providing a predetermined drag on said arbor, two brackets carried by the table and adjustably positionable circumferentially of the table at equal radial distances from the axis through the centers, a finger pivotally supported intermediate its ends in each bracket to move in a plane parallel to the table, spring means biasing said fingers to normally hold them radially of the table, the inner ends of said fingersbeing adapted to contact respectively the corresponding faces of the teeth on a gear-shaped member between which the space is to be checked, a stop engaging the outer end of one of the fingers and preventing motion in one direction, an indicating mechanism operatively associated with the outer end of the other finger, and means for indexing the gear-shaped member on the arbor to present successive spaces between the predetermined number of teeth to the inner ends of the two spaced pivoted fingers.

5. A device for checking or comparing the pitch of substantially equally spaced teeth on a gear-like member, said device comprising means for rotatably supporting the gear-like member to be checked, an indicating mechanism, two pivoted fingers mounted for independent adjustment circumferentially relatively to each other at equal radial distances from the axis upon which the gear-like member is supportable to span a predetermined plurality of teeth on such member up to minus one tooth for contacting respectively the corresponding faces of the spanned terminal teeth, on said gear-like member upon which the space is to be checked, one of said fingers constituting a stop, the other of said fingers being movable and cooperating with the indicating mechanism, the means for rotatably supporting the gear-like member comprising adjustable, spring-loaded means for enclosing a variable amount of drag on the rotation of said gear-like member, mechanical means for indexing the gear-like member to present successive spaces between the predetermined spanned number of teeth to the two spaced fingers, and both fingers being adapted to ride over the teeth during the indexing operation.

GUSTAVE H. HEDMAN.

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